At centenary celebrations thrown for the author on Sunday, writers and publishers traded questions. Who was the seller? And how did they obtain this collection, which includes family photographs, early manuscripts, late work, and 100 pages of an unpublished novel? It quickly became clear that Mahfouz's immediate family – his wife and two daughters – were unaware of the sale.

Nor were Sotheby's able to shed any light. Spokesperson Leyla Daybelge responded to enquiries via email, saying only that "the Mahfouz archive is being sold by a private source in North America and the timing coinciding with the author's centenary is coincidental". The auction house offered no further identification of the provenance of the materials, although they did tweet in response to repeated questions: "We take provenance seriously+investigated this archive before offering it. It was lawfully purchased from owners close to Mahfouz."

This response did not, however, satisfy the Egyptian authors, publishers, and booksellers who have expressed dismay over the sale. Editor and author Rehab Bassam responded, on Twitter: "so how come his family doesn't know??" Prominent Mahfouz scholar Rasheed al-Enany was forceful in defense of bringing the archive back to Egypt. "I am disturbed to see this national treasure go out of its natural habitat, its very source of inspiration: Egypt," he said. "I think Mahfouz was once described as Egypt's fourth pyramid. To extend the metaphor, I'm saying someone has smuggled one of Egypt's pyramids out of the country and is putting it up for sale."

Bassam said that she had spoken with Mahfouz's daughter, and that the family had been told that "everybody is intervening" to stop the sale, including "Amr Moussa, the Egyptian ambassador in London, the minister of culture, a former minister of culture and a list of other names." The family believed that Sotheby's had no right to sell the materials in question "because they didn't acquire them from the family, which has the sole rights to sell such things." Journalist Mohammad Shoair noted in the Beirut-based newspaper Al Akhbar that some archival material had been illegally taken from the Mahfouz family home in the past. Mahfouz translator and biographer Raymond Stock was similarly unaware of the provenance of the items, but said that he and a friend had previously been working with a New York book dealer to acquire items for what they believed, he said, was a university archive of Mahfouz's works.

But other authors were less concerned with the provenance than with the need to see the materials returned to Egypt. Prominent Egyptian novelist Mansoura Ezz Eldin expressed the hope that the archives could be bought by the Egyptian Ministry of Culture or by the American University in Cairo (AUC) Press. However, although the archive's price tag – a recommended £50,000 to £70,000 – was set lower than other literary items on sale in the auction, which is to take place on 15 December, the AUC Press and culture ministry have said they lack the funds to bid on the archive.

The collection was assessed for Sotheby's by Alyn Hine, a PhD candidate at London's School for Oriental and African Studies. He too was not given any information about their provenance, but said that "it's always hugely exciting to hold in your hands the original writings of any significant author, especially one as highly regarded as Mahfouz".

Also included in the archive is the unpublished draft of a novel titled "Story of the Sudan". Hine believed the draft, which he speculated might be related to Mahfouz's popular Cairo Trilogy, would "be of more interest to scholars than readers ... I know how frustrating it can be, as a reader, to read something that is incomplete. However, it would depend on what a skilled editor could achieve with the material."

Of all the materials, Hine said, "the 'Sudan' story and the 'Dreams' manuscripts are the main items ... They both demonstrate how a great writer works. Someone familiar with Mahfouz's biography would gain a great deal of insight into how he crafted his literary works by looking at those two manuscripts."